1. Field of the Invention
The present invention pertains to a mechanical coupling or connection for joining rigid tubes together and methods of constructing same. More particularly, the present invention pertains to a mechanically crimped connection for directly joining two rigid (typically metal) tubes together, which connection can withstand axial, radial and rotational forces and may be substantially fluid-tight, and to methods of constructing same.
2. Description of Relevant Art
There are known connections for joining rigid tubes, or tubular components, together, such known connections including brazed, welded or soldered joints, threaded fittings, compression fittings, etc. As used throughout this application, the language "tube" and "tubular component" are used interchangeably to define any component having at least one tubular end portion.
With reference to FIG. 1a of the accompanying drawings, for example, there is shown a threaded connection for two tubular metal components which is and has widely been used in the automotive industries in vehicle emissions systems. In the drawing there is shown a valve member 1 with a metal casing 2, the metal casing having an extruded tubular fitting 4 at one end and a threaded metal connection 6 at the other end thereof. Also shown in FIG. 1 is a rigid metal tube 8 having a threaded fitting 10 at one end thereof and which is adapted to mate with the fitting 6 provided on the valve casing 2, and whereby the fittings 6, 10 function as a substantially fluid-tight connection for two metal tubular components, i.e., one end of the metal valve casing 2 and the metal tube 8. The order of the fittings 6, 10 could be reversed, i.e., such that the female fitting 6 is provided on the tube 8 and the male fitting 10 is provided on the casing 12. Typically the fitting 6 or 10 provided on the casing 12 is formed of low-carbon steel and is crimped to the casing 12, while the fitting on the tube 8 is formed of stainless steel and is welded or brazed to the tube.
Although the threaded connection as shown in FIG. 1 is used extensively today, especially in many high temperature applications where it is not desirable to use a connection having rubber or plastic components, the connection has many problems and disadvantages associated therewith. For example, use of a threaded connection is very expensive not only because the fittings 6, 10 are expensive to manufacture, typically requiring machining, but also because the fittings must be connected to respective tubular members as discussed above, and because joining of the threaded fittings 6, 10 as part of a larger device is labor intensive. In the automotive industry, for example, the fittings 6, 10 would typically be screwed together as a vehicle moves along the assembly line.
Furthermore, the structural nature of the threaded fittings 6, 10 necessarily results in quality control problems, which of course lead to increased warranty costs for makers and sellers of devices using the threaded connections. For example, there is a risk of fluid leaks when using a threaded connection because fluid may leak not only through and around the coupled threads of the fittings, but may also leak at either of the joints, which are typically crimped, welded or brazed, between the threaded fittings and the respective tubular members. Relatedly, tubular joints using such threaded connections may tend to corrode and prematurely fail at any or all of these same three areas. Correspondingly, any quality control program must separately consider each of the three potential areas of fluid leaks.
Many of the above problems and disadvantages also occur when metal tubes are joined together through brazing, soldering or welding without threaded fittings, especially those problems and disadvantages relating to corrosion, fluid leakage and labor requirements needed to effect the connections. Relatedly, although some metals, such as stainless steel, are inherently corrosion resistant and do not require corrosion preventing finishes applied thereto, such metals are typically extremely difficult to braze, solder or weld.
Referring to FIG. 1b, there is shown a known compression type connection 101 which is conventionally used for joining rigid tubular components together, the connection being conventionally referred to as a U-Bolt clamp. The connection 101 comprises a rigid metal ring 102 which would be fitted over the mated end portions of two tubular components and a screw mechanism 104 associated with the ring 102 for tightening same and thereby compressing the tube end portions together. In this regard, to such known compression connection, there are again various problems and disadvantages associated therewith. For example, the U-Bolt clamp, like the threaded connection of FIG. 1a, is relatively expensive not only because the clamp itself is expensive, but also because the process of applying the clamp to two tubular components is relatively labor intensive. Also, the action of tightening the screw mechanism 104 to achieve the necessary connection is difficult to precisely control, so that the precise degree of fluid-tightness associated with the connection may vary to some extent from connection to connection.
In an effort to overcome the foregoing problems and disadvantages of known connections for joining rigid tubular components, applicant has previously proposed a connection, such as shown in FIG. 2 of the present application, for joining two tubular components formed of low-carbon steel and for joining a tubular component of low-carbon steel to another tubular component of stainless steel. The carbon steel components are provided with an aluminized coating.
With reference to FIG. 2, a valve device 11 has one end of a casing 12 thereof (which has been extruded into a tubular shape) directly joined to the end portion of a tube 14 through a pair of circumferential crimps 16. The casing 12 may be formed of either low-carbon steel or stainless steel and the tube 14 is formed of low-carbon steel. The end portion of the tube 14 is expanded over the end 12 of the valve device, and the crimps 16 (each of which comprises a series of uniform rectangular recesses spaced completely around the circumference of the tubular components) distort or compress portions of the tubular components inwardly and against each other. The crimps 16 function to hold the two tubular components in a fixed relationship to each other and to form a substantially fluid-tight seal therebetween. Such crimps have previously been used for joining a rigid metal tubular component to another tubular component formed of a non-rigid material such as rubber. U.S. Pat. No. 4,690,435, for example, discloses a crimp connection for joining a rubber hose to a metal fitting.
Applicant's previously proposed crimped connection functions very well and represents a significant advancement over known connections for joining rigid tubular components, however, improvements may be necessary as new system requirements become evident.
Specifically regarding applicability, many industries such as the automotive industry now utilize tubular components formed of various metals instead of low-carbon steel, including many corrosion resistant metals such as stainless steel, and of a variety of wall thicknesses, and applicant has discovered that the previous crimped connection cannot be applied to each of the various applications involving the different metals without significant modifications/adaptations specific to each particular application. For example, the low-carbon steel used in the previously proposed crimped connection is easily deformable and can form a relatively high quality seal between two tubular components under a relatively wide range of conditions, whereas stainless steel (which is now required for use in many automotive applications because of its corrosion resistance) is a relatively hard material which can be properly deformed only under a relatively narrow range of conditions.
The present invention has been developed to overcome the foregoing limitations, problems and disadvantages associated with known connections for connecting rigid tubular components, and to generally fulfill a great need in the art for a simple, high quality connection for joining two tubular metal components which can be rapidly effected for simple high quality, more consistent connection.